Nature Publishing Group, publisher of Nature, and other science journals and reference works
my account e-alerts subscribe register
Tuesday 17 October 2017
Journal Home
Current Issue
Download PDF
Export citation
Export references
Send to a friend
More articles like this

Letters to Nature
Nature 374, 39 - 41 (02 March 1994); doi:10.1038/374039a0

Avalanche mixing of granular solids

Guy Metcalfe, Troy Shinbrot, J. J. McCarthy & Julio M. Ottino*

Department of Chemical Engineering, Northwestern University, Evanston, Illinois 60208-3120, USA
* To whom correspondence should be addressed.

THE production of many goods, ranging from pharmaceuticals and foods to polymers and semiconductors, depends on reliable, uniform mixing of solids. Although there have been several notable recent advances1–6, solid mixing processes are still poorly understood. We can neither qualitatively nor quantitively determine the effectiveness of any given mixing process in advance. In contrast to the case of liquid mixing7, we do not have a widely accepted theoretical basis that describes the mixing of solids. Moreover, we cannot determine whether a given set of solids will mix or separate during a specified stirring process8–23. As a step towards uncovering the basic physical principles, it is helpful to analyse systems that are both experimentally and theoretically tractable. Here we describe a geometric technique for the analysis of slow granular mixing processes, as are commonly encountered in industry. By comparing our calculations with experiments on thin rotating containers partially filled with coloured particles, we demonstrate that the mixing behaviour of powders in slow flows can be divided into geometric and dynamic parts. For monodisperse, weakly cohesive particles, geometric aspects dominate.

© 1994 Nature Publishing Group
Privacy Policy